Petroleum refining and petrochemical processing units frequently utilized an atmospheric fractionation column for separating a feed, such as crude oil or condensate from natural gas, into multiple streams such as light ends, naphtha, distillate (kerosene and/or diesel), and atmospheric residue. The naphtha stream may be separated into a liquid petroleum gas (LPG) and naphtha in a light ends column (stabilizer). After separation, the naphtha and distillate are then separately hydrotreated for the production of low sulfur fuels (e.g. diesel) and as pretreatment for further refining processes (e.g. naphtha to reforming and isomerization for gasoline production).
For small refineries which may be designed and constructed as modular refineries, the naphtha and distillate streams can be hydrotreated in a combined unit. An example of such a refinery is one which processes shale gas condensates, but other condensates, light crudes, and even heavier crudes could be suitable feeds for such a modular refinery with a combined hydrotreating unit.
One potential drawback associated with combined hydrotreating is that naphtha and distillate products must be separated after hydrotreating. While some separation of the feed streams into multiple streams is desired to remove light components, such as LPG, or heavier residue, the current upstream separation provides large fractionations sections that are expensive to build. Furthermore, these separation sections are typically operated in such a manner that provides stringent separation of the distillate and naphtha products which is energy intensive and expensive to operate. However, since these streams are combined in a combined hydrotreating unit, high quality separation upstream of the hydrotreating unit results in unnecessary use of capital and energy.
Therefore, there remains a need for an effective and efficient process for separating the feed stream for a combined hydrotreating unit.